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The grooves for the pistons rings are machined deeper than the ring thickness so rings can be compressed inwards deeper than the outside diameter which is also much smaller than the bore where the rings fit.
One of the most difficult things for specialists to deal with are serious problems that only afflict a small number of cars (as in the 9A1 Gen 2 bore scoring saga because both the individual specialists and as a group - get to see far fewer and it takes longer to see different failure modes. It is much easier to analyse and work out the causes when there are a lot that are exactly the same.
Up until now the only ones we have seen are 3.8's all like the picture recently posted, but scored on both sides of the piston and bore - hence not "scoring" but "seizing" because the piston has grown bigger than the bore. Reasons for this can be age related stress relieving, piston getting too hot (all sorts of explanations with fuelling, ignition and coolant problems) etc.
When they seize it is usually creating deep grooves - like the recent picture shows on one side of the bore - which is why I would like to see a picture showing both sides to see if it was a seizure or scoring (and the same request applies to the piston).
Measuring the cylinders near the scored ones - they all had shrunk in at the bottom from the already very tight clearances run on this engine. With the very heavy cross section of the aluminium part of the casting at the bottom of the bores being the slowest to heat up (compared to pistons or bore areas with coolant nearby) the bottom of the cylinders would seize first and the lines would ne nearer the bottom than the top.
However - further information that has come to light would suggest that there are 2 types of bore failures - because I have now seen a picture of a 3.6 that has scored on one side only. These scores were all across the circumference (not in line with those heavy cast areas) right from one side of the skirt to the other while the opposite side of the bore and piston showed light scoring. I am not sure at this stage if the cause might have been due to low oil levels and will keep you informed as and when I find out more.
It could therefore be that some engines have scored and some seized (we have only seen the latter) and it is very valuable if we can verify which failure mode we are dealing with and if there is a proportion in numbers of each type - for which a forum like this could be invaluable if only specialists would just present these simple answers instead of launching into too much technical detail moving the goal posts.
So if you have seen these failures please post if they have been scored/seized both sides or one side or of you have seen both - at what proportions/percentages - in numbers.
The 3.6 has even thicker cast areas round that actual bore (since the bore is only 97mm instead of the 102mm of the 3.8) and this may help stabilise the bore and reduce any distortion on this model - so this scoring event I have just seen may be a different failure to the 3.8's.
In our experience the vast majority of Porsche buyers do not research the reliability of the cars before purchasing and although there could be a small influence on values if they have a proven reputation for a problem - the numbers are too small with the Gen 2 and the fact that better quality repairs are available from specialists at lower costs than a replacement engine can elevate demand so the benefit of posting information is for those that do research and those and find they experience problem - providing options for them to consider.
The manufacturers get the earliest warning if there product has a significant issue (because most new cars are serviced by their organisations in the first few years (5-6 years usually in the UK) so specialists not only learn about issues later but see far fewer from which to base their opinions and decisions to invest or not in solutions - and the more they can communicate - the better - for which forums like this can be invaluable - if they simply post information without commercial connections or rivalry getting in the way.
Well that's my opinion anyway - and why I have already sent detailed technical information to Charles and Jake without yet receiving anything back.
The grooves for the pistons rings are machined deeper than the ring thickness so rings can be compressed inwards deeper than the outside diameter which is also much smaller than the bore where the rings fit.
One of the most difficult things for specialists to deal with are serious problems that only afflict a small number of cars (as in the 9A1 Gen 2 bore scoring saga because both the individual specialists and as a group - get to see far fewer and it takes longer to see different failure modes. It is much easier to analyse and work out the causes when there are a lot that are exactly the same.
Up until now the only ones we have seen are 3.8's all like the picture recently posted, but scored on both sides of the piston and bore - hence not "scoring" but "seizing" because the piston has grown bigger than the bore. Reasons for this can be age related stress relieving, piston getting too hot (all sorts of explanations with fuelling, ignition and coolant problems) etc.
When they seize it is usually creating deep grooves - like the recent picture shows on one side of the bore - which is why I would like to see a picture showing both sides to see if it was a seizure or scoring (and the same request applies to the piston).
Measuring the cylinders near the scored ones - they all had shrunk in at the bottom from the already very tight clearances run on this engine. With the very heavy cross section of the aluminium part of the casting at the bottom of the bores being the slowest to heat up (compared to pistons or bore areas with coolant nearby) the bottom of the cylinders would seize first and the lines would ne nearer the bottom than the top.
However - further information that has come to light would suggest that there are 2 types of bore failures - because I have now seen a picture of a 3.6 that has scored on one side only. These scores were all across the circumference (not in line with those heavy cast areas) right from one side of the skirt to the other while the opposite side of the bore and piston showed light scoring. I am not sure at this stage if the cause might have been due to low oil levels and will keep you informed as and when I find out more.
It could therefore be that some engines have scored and some seized (we have only seen the latter) and it is very valuable if we can verify which failure mode we are dealing with and if there is a proportion in numbers of each type - for which a forum like this could be invaluable if only specialists would just present these simple answers instead of launching into too much technical detail moving the goal posts.
So if you have seen these failures please post if they have been scored/seized both sides or one side or of you have seen both - at what proportions/percentages - in numbers.
The 3.6 has even thicker cast areas round that actual bore (since the bore is only 97mm instead of the 102mm of the 3.8) and this may help stabilise the bore and reduce any distortion on this model - so this scoring event I have just seen may be a different failure to the 3.8's.
In our experience the vast majority of Porsche buyers do not research the reliability of the cars before purchasing and although there could be a small influence on values if they have a proven reputation for a problem - the numbers are too small with the Gen 2 and the fact that better quality repairs are available from specialists at lower costs than a replacement engine can elevate demand so the benefit of posting information is for those that do research and those and find they experience problem - providing options for them to consider.
The manufacturers get the earliest warning if there product has a significant issue (because most new cars are serviced by their organisations in the first few years (5-6 years usually in the UK) so specialists not only learn about issues later but see far fewer from which to base their opinions and decisions to invest or not in solutions - and the more they can communicate - the better - for which forums like this can be invaluable - if they simply post information without commercial connections or rivalry getting in the way.
Well that's my opinion anyway - and why I have already sent detailed technical information to Charles and Jake without yet receiving anything back.
Baz
Thank you for sharing. There is no rivalry here and I have little to gain from my time spent researching this topic because, as I have stated before, failures of these engines are far and few between. With such a small data set, all you can do is measure everything and come up with possible scenarios for what may or may not have happened.
You must have emailed Jake alone, as the last email I have from you is from 5/12/2017. I would be interested to see what other data you have or if you would post it as I did with all the measurements provided from Bronz's block, that would benefit all interested in wrapping their heads around this phenomenon.
Here I have been mistaking scoring and seizing. It seems it is more proper to say seizing if there is "scoring" on both sides and scoring if only one side, no? Seems the fix for both is similar or same and beyond the minimum to fix damaged parts including Nickies if chosen for bore replacement, one can upgrade other parts or not.
Here I have been mistaking scoring and seizing. It seems it is more proper to say seizing if there is "scoring" on both sides and scoring if only one side, no? Seems the fix for both is similar or same and beyond the minimum to fix damaged parts including Nickies if chosen for bore replacement, one can upgrade other parts or not.
Smart man.
I'd rather Nick-a-seal, than Lok-a-seal or let a-loose-a-seal any day. Please forgive the phonics.
Yes C4SDayton - M96/7 Gen 1 there is almost always just cracking or "D" chunking in early 3.4 engines with ferrous coated pistons and scoring in later 3.4, 3.6 and 3.8 engines with plastic coated pistons - but there are 2 possible failure modes now for 9A1 Gen 2 engines - seizing (which is all we have physically seen) and scoring of 3.6 Gen 2 (which we have only seen photos of).
The Gen 2's that we have physically measured all closed in at the bottom of the cylinders and seized early in the warm up cycle following aggressive driving from cold and in relatively cold ambient conditions.
Charles - I agree that the numbers of Gen 2 failures are small but we feel we still have to investigate the causes because they were small when they first started in the Gen 1 engines and we got in early, identified the causes quickly, designed a remedy, invested in production, tested it early and ever since have been able to offer an excellent repair option which has benefitted countless owners (similar to what you did over there initially I believe).
Although we have not seen many Gen 2 failures - up until now they have been consistent and resulted in good advice to owners about warm up procedures and incentivising us to carry out testing of repair options.
I sent Jake information about piston shapes, bore measurements, photos etc to help add to the information available as his own reports didn't seem to cover the same topics as we had been investigating - from which he said he was sending you the parts to measure and I assumed this meant that he would also send you the technical information that I sent him and that you were both working together on the problem - sorry if that reasonable assumption was wrong and I implied otherwise.
There will be different scenarios and different contributory factors and causes (not to mention different conditions and/or fuel and ambient factors in the UK and USA) and so I didn't post the information on here as it could have contradicted what Jake seemed to have concentrated on as the causes and preferred for us to share our research and mutually understand the issues before hopefully agreeing on some sort of joint understanding of different contributory factors so that readers and owners receive consistent information that they can trust rather than being forced to make choices. As yet I have not seen a reply.
Following some external interference in our computer network and present security changes - I cannot access that information (or some E-mails) until mid next week and in the meantime if he doesn't send it on to you - I will.
For present owners the incidences are indeed very low and the warming up delays for a minimum of 10 minutes (and preferably 20 minutes) before driving hard - are in my opinion, very good and relevant advice that may prevent some failures and reduce the numbers even further. Meanwhile we sill continue to develop a solution so that when the small number do fail (or if and when the numbers increase with age and mileage) we are ready to respond.
Yes C4SDayton - M96/7 Gen 1 there is almost always just cracking or "D" chunking in early 3.4 engines with ferrous coated pistons and scoring in later 3.4, 3.6 and 3.8 engines with plastic coated pistons - but there are 2 possible failure modes now for 9A1 Gen 2 engines - seizing (which is all we have physically seen) and scoring of 3.6 Gen 2 (which we have only seen photos of).
The Gen 2's that we have physically measured all closed in at the bottom of the cylinders and seized early in the warm up cycle following aggressive driving from cold and in relatively cold ambient conditions.
Charles - I agree that the numbers of Gen 2 failures are small but we feel we still have to investigate the causes because they were small when they first started in the Gen 1 engines and we got in early, identified the causes quickly, designed a remedy, invested in production, tested it early and ever since have been able to offer an excellent repair option which has benefitted countless owners (similar to what you did over there initially I believe).
Although we have not seen many Gen 2 failures - up until now they have been consistent and resulted in good advice to owners about warm up procedures and incentivising us to carry out testing of repair options.
I sent Jake information about piston shapes, bore measurements, photos etc to help add to the information available as his own reports didn't seem to cover the same topics as we had been investigating - from which he said he was sending you the parts to measure and I assumed this meant that he would also send you the technical information that I sent him and that you were both working together on the problem - sorry if that reasonable assumption was wrong and I implied otherwise.
There will be different scenarios and different contributory factors and causes (not to mention different conditions and/or fuel and ambient factors in the UK and USA) and so I didn't post the information on here as it could have contradicted what Jake seemed to have concentrated on as the causes and preferred for us to share our research and mutually understand the issues before hopefully agreeing on some sort of joint understanding of different contributory factors so that readers and owners receive consistent information that they can trust rather than being forced to make choices. As yet I have not seen a reply.
Following some external interference in our computer network and present security changes - I cannot access that information (or some E-mails) until mid next week and in the meantime if he doesn't send it on to you - I will.
For present owners the incidences are indeed very low and the warming up delays for a minimum of 10 minutes (and preferably 20 minutes) before driving hard - are in my opinion, very good and relevant advice that may prevent some failures and reduce the numbers even further. Meanwhile we sill continue to develop a solution so that when the small number do fail (or if and when the numbers increase with age and mileage) we are ready to respond.
Regards,
Baz
Although Jake and I collaborate on development projects and I sleeve all the blocks for his builds, we are indeed separate entities. I did not see any correspondence from Jake on this subject other than his request for us to do a failure analysis of Bronz's components. Please do forward anything you have that you would like to me to look at. I don't have anything else to share beyond what is already shared on this thread and the 2009 C4S 3.8 scored bores photos I had posted on the 991 bore score thread previously.
Lets see, after 45 pages and scaring all the 997.2 owners ****less on bore scoring, are we finally settling on a non-relevant issue that its a rare case of cylinder/piston seizure ?
How many engineers does it take to change a light bulb?
Answer.... None. Because Darkness is the new standard !!
Lets see, after 45 pages and scaring all the 997.2 owners ****less on bore scoring, are we finally settling on a non-relevant issue that its a rare case of cylinder/piston seizure ?
How many engineers does it take to change a light bulb?
Answer.... None. Because Darkness is the new standard !!
I don't think that's exactly the case. Rare, yes, but I think many of us (except Baz) were using the term bore scoring in broader terms anytime we saw damage to the cylinder walls. Baz is just separating the cylinder wall damage into two different categories - scoring and seizing, and if I've been keeping up, the cylinder constriction at the case is the cause of the seizing and he has seen this in all his cases, be those rather few. So the failure mode on the 997.1 engines seems to be scoring, whereas on the 997.2 it's seizing. You can name it whatever you like, but the engine is still coming apart to rectify it.
As I haven't shared these previously on this thread (and I apologize for the Mr. Blurry Cam photos), these are from back in 2011. 2009 C4S 3.8:
So yes, scoring is possible, but as stated early, not very common. An engine with Alusil is susceptible to scoring by the very nature of its design. Just Google BMW or Mercedes and Alusil Scoring and you'll find more examples.
What is being glazed over in this very technical discussion is that there are steps that should be taken to help prevent this. Isn't that the purpose of this discussion - to help those interested in the topic understand the problem and come up with a solution?
...Isn't that the purpose of this discussion - to help those interested in the topic understand the problem and come up with a solution?
From my foxhole, yes, that is the purpose of this discussion. And many thanks to you, Baz, and Jake for your contributions to all things Porsche engine.
Just a general observation as a Porsche newbie, Ive found this thread fascinating and informative so in my appreciation to all those that took the time to post - TY!
Let me preface my post with the fact that I appreciate professionals taking the time to post on a forum. I think everyone agrees on the purpose of the thread. I just think it's counterproductive to keep bringing up issues that didn't contribute to the failure of this engine. It keeps the thread going around in circles and misinforming people. If we can establish the reason the engine failed and eliminate issues that did not the cause of the failure, then we can drill down to the real issues we need to be concerned with.
Cause of failure
Can we establish that this engine was a cold seizure failure?
Baz has stated that all of the engines that he has repaired "seized early in the warm up cycle" and that this engine seems to have the same failure mode. Jake also concurred that his pics of the failures he's seen are very similar to Baz's. (Forget the pics you just posted of a 8 year old failure for the moment)
Not related to the failure
Right now there are 3 issues that I believe are not related to the failure of the engine and I wish could be put to rest by Jake or Charles. If I'm wrong, no worries post up the evidence.
1. LSPI - I've seen no evidence of LSPI with this failure. Forget about if you can hear it or not. The point with LSPI is it's a major concern for some engines because when it actually happens it damages engine parts. It's not about bearing wear.
2. Fuel Injector Failure - I don't see evidence of fuel wash and no one has come on here and said they tested the injector and it was bad.
3. Alusil failure - This failure looks like a cold seizure. It doesn't matter what material you use if the piston is too big for the bore and it seizes.
As I haven't shared these previously on this thread (and I apologize for the Mr. Blurry Cam photos), these are from back in 2011. 2009 C4S 3.8:
So yes, scoring is possible, but as stated early, not very common. An engine with Alusil is susceptible to scoring by the very nature of its design. Just Google BMW or Mercedes and Alusil Scoring and you'll find more examples.
What is being glazed over in this very technical discussion is that there are steps that should be taken to help prevent this. Isn't that the purpose of this discussion - to help those interested in the topic understand the problem and come up with a solution?
Do you know where this car spent most of its life? Seems to be a lot of consensus (right or wrong) that cars living in colder climate are more prone to scoring than southern cars. Any opinion on this?
04-24-2019, 05:03 AM
